Fatigue Flashcards
Def: Fatigue
a decrease in force or power generating capacity
How does fatigue affect isometric contractions
-reduced force
-reduced rate of force development
-reduced rate of force relaxation
How does fatigue affect concentric contractions
-reduced force
-reduced velocity
(reduced power)
How does fatigue affect eccentric contractions
-reduced force
-reduced velocity
(reduced power)
Why is there not a linear relationship between endurance and % ISO MVC
with greater % ISO MAX, there is a greater effect of occlusion causing a greater decrease in endurance
Compare how fatigue is observed in a MVC vs a submaximal contraction
MVC: start at peak force then decline in force due to fatigue almost immediately observed until complete drop at failure
SUBMAXIMAL: maintain consistent submax force until decline in force that you are able to produce due to fatigue meets force of submax then failure occurs
What is the effect of fatigue on the force velocity relationship
There will be a decline in the ISOmax due to a decreased number of active CB and a decline in Vmax due to a decrease in the rate of CB cycling
Peripheral regions that can be affected during fatigue
Motoneurons, Neuromuscular junction, muscle fibers, Cross-bridge
Cause and pathway of central fatigue
CAUSE:
-failure of volition/ lack of drive
-decreased neurotransmitter concentration
-increased metabolites
-hypoglycemia
-decreased membrane excitability
PATHWAY:
MU drop out = decreased activated fibers = active CB = less force capacity
AND
decrease FR= less summation = decreased activated CB = less force capacity
Cause of motoneuron fatigue
-decreased excitability of motoneurons
-reflex inhibition from metabolites
Neuromuscular junction fatigue
-Ach depletion
-reduced endplate excitability
factors causing excitation-contraction coupling failure
-fuel depletion
-accumulation of metabolites
How does fuel depletion cause fatigue
DECREASE IN ATP
-decreased sensitivity of Ca2+ channels leading to a decrease in the amount of Ca2+ released through the SR resulting in an overall decrease in CB activity
DECREASE IN GLYCOGEN
-decreased sensitivity of Ca2+ channels leading to a decrease in the amount of Ca2+ released through the SR resulting in an overall decrease in CB activity
How does the accumulation of metabolites cause fatigue
ACCUMULATION OF Pi
-decreased sensitivity of Ca2+ channels leading to a decrease in the amount of Ca2+ released through the SR resulting in an overall decrease in CB activity
ACCUMULATION OF H+ ION
-interference with Ca2+ binding troponin leading to a decrease in CB activation
-Decrease in pH may also inhibit release of Ca2+
Factors causing fatigue directly to the CB
DECREASED # OF ACTIVE CB
-decreased ATP prevents full capacity CB cycling
FORCE PER CB
-increased Pi causes a decrease in bond strength and increases the likelihood of detachment
-increased Pi cause a decrease in Ca+/troponin interaction causing an increased requirement of Ca2+
SLOWER ADP RELEASE DURING CB CYCLING
-increased H+ ion may cause slower release
In high intensity isometric training, what factors are going to contribute to fatigue
limited O2
decrease in ATP
decrease in PCr
increases in Pi
increase in H+ ion
In high intensity exercise lasting 4-5 minutes, what factors are going to contribute to fatigue
limited O2
decreased ATP
decreased PCr
increased Pi
increased H+
decrease in glycogen will contribute to an extent
In low intensity exercise lasting around 2 hours, what factors are likely to contribute to fatigue
decrease in glycogen
decrease in hypoglycemia
decreased hydration
increased hyperthermia
limited O2